This invention relates to shaker conveyors of the type commonly used for transferring scrap pieces of metal from a mechanical press to a collection container and as disclosed, for example, in U.S. Pat. No. 6,415,912, U.S. Pat. No. 6,634,488 and in published patent applications No. 2007/0017783 and No. 2008/0245639. However, such shaker conveyors may also be progressively transferring other articles along a generally horizontal path. In such conveyors, one or more horizontal elongated trays are reciprocated at a frequency or speed and with a motion that the pieces or articles are progressively advanced along each tray. Shaker conveyors are commonly described as having a motion where the tray and the material to be conveyed move in one direction together and then the tray is rapidly moved in the opposite direction making the material slip relative to the tray. The slippage usually occurs after the tray has been reversed with the result that the material starts moving in the reverse direction before slipping.
It has been found that a shaker conveyor will operate better when the material or articles being conveyed begin to slide forward relative to the tray just before the end of the forward stroke. As a result, the material or articles continue to slide in the forward direction when the tray has reached the end of the stroke and is quickly accelerated in the opposite direction. When a shaker conveyor is used on a mechanical press, it is desirable for the conveyor to be a compact unit supported by the press and be easily attached and removed from the press for use on another press or for servicing. Also, when a plurality of parallel spaced trays are used on a press, it is desirable to apply the force which reciprocates the trays at a center location which is symmetrical with all of the trays. It is also desirable for multiple trays to be easily and conveniently removed and repositioned in parallel spaced relation to accommodate different progressive dies or tooling on a press or on different presses.